Struct SpeedSmoother 

pub struct SpeedSmoother { /* private fields */ }

Speed smoother using Exponential Moving Average (EMA) algorithm.

This struct provides smoothed download/upload speed calculations that:

• Reduce noise from fluctuating network conditions
• React quickly to sustained speed changes
• Detect temporary bursts vs sustained speed changes
• Calculate accurate ETA estimates

Algorithm

Uses EMA with configurable window size N:

alpha = 2 / (N + 1)
EMA_new = alpha * value + (1 - alpha) * EMA_old

Larger N values provide more smoothing but slower reaction to changes. Default N=10 provides good balance for typical download scenarios.

Example Usage

use aria2_core::util::speed_smooth::SpeedSmoother;

let mut smoother = SpeedSmoother::new(10);
smoother.record_bytes(1024); // Record 1KB downloaded
// ... after some time ...
let speed = smoother.smoothed_speed();
let remaining_bytes = 50000u64;
let eta = smoother.eta_seconds(remaining_bytes);

Implementations

impl SpeedSmoother

pub fn new(window_size: usize) -> Self

Create a new SpeedSmoother with specified window size.

Arguments

• window_size - Number of samples for EMA window (default: 10)

The alpha smoothing factor is calculated as 2 / (N + 1) where N is the window size. Larger values provide more smoothing.

pub fn with_default_window() -> Self

Create a SpeedSmoother with default window size (N=10).

pub fn record_bytes(&mut self, bytes: u64)

Record bytes transferred and potentially update EMA.

Bytes are accumulated until the sample interval (500ms) has elapsed, at which point the instantaneous speed is calculated and used to update the EMA value.

Arguments

• bytes - Number of bytes transferred since last call

pub fn smoothed_speed(&self) -> f64

Get the current EMA-smoothed speed in bytes per second.

Returns the smoothed speed value, clamped to non-negative. If no samples have been recorded yet, returns 0.0.

pub fn instant_speed(&self) -> f64

Get the instantaneous (raw) speed from current sample window.

Calculates speed based on bytes accumulated so far in the current sampling interval. Returns the last calculated instant speed if no data has been accumulated in the current window.

pub fn eta_seconds(&self, remaining: u64) -> Option<u64>

Calculate ETA in seconds for remaining bytes at current smoothed speed.

Arguments

• remaining - Number of bytes still to download/upload

Returns

• Some(seconds) - Estimated time remaining if speed > 0
• None - Cannot calculate (speed is zero or negative)

pub fn is_burst(&self) -> bool

Check if current speed indicates a burst condition.

A burst is detected when the instantaneous speed exceeds BURST_THRESHOLD_MULTIPLIER (3x) times the smoothed EMA speed. This can indicate temporary buffer flushes or compression artifacts.

pub fn reset(&mut self)

Reset all internal state to initial values.

Clears all accumulators, counters, and timestamps. Useful when starting a new download or after a pause/resume.

pub fn samples_count(&self) -> usize

Get the number of samples processed so far.

pub fn alpha(&self) -> f64

Get the current alpha smoothing factor.

Trait Implementations

impl Default for SpeedSmoother

fn default() -> Self

Returns the “default value” for a type.